Ossification of the posterior longitudinal ligament in evolution in 12 patients.

Ossification of the posterior longitudinal ligament (OPLL) in evolution (OEV), an early form of OPLL, was newly discovered in 12 of 43 (28%) patients who had OPLL and underwent operations from 1989-1992. Magnetic resonance imaging and CT studies of OEV patients who were younger, in their mid-forties, and had less severe spastic myeloradiculopathy, showed hypertrophied posterior longitudinal ligaments containing punctate ossification at disc spaces and contiguous endplates, with occasional extension behind vertebral bodies. However, both location and neuroradiologic appearance allowed OEV to be confused readily with disc or spondylotic disease. Only heightened awareness of the clinical and radiographic findings of OEV allowed the correct diagnosis. The appropriately extended anterior discectomies or corpectomies with fusions contributed to better outcomes.